Are There Side Effects to Drinking a Gallon of Milk a Day?

Drinking a gallon of milk each day could cause long-term health issues.

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According to the USDA Economic Research Service, milk and cream are the most popularly consumed milk products in the United States. While regular consumption of milk and other dairy products is recommended, a gallon of milk a day is an excessive amount. Drinking large amounts of milk every day can have long-term negative effects on your health.

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Drinking a gallon of milk every day would result in excessive consumption of calories and certain nutrients, like protein. Long-term consumption of too much milk can cause health issues and even increased risk of mortality.

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Consuming Milk and Milk Products

Regardless of whether you're a young person or an older adult, milk is considered to be a healthy, nutrient-rich food. However, the side effects of drinking milk are correlated with the type of milk product you've chosen. You can typically find skim milk, 1 percent milk, 2 percent milk and full-fat cow's milk sold in stores.

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The Dietary Guidelines for Americans recommends consuming fat-free and low-fat dairy products such as milk, yogurt and cheese on a daily basis. Excessive consumption of higher-fat products can trigger an inflammatory response from your immune system and are considered to be bad for the health of your heart.

Side Effects Associated With Milk

Milk is considered to be healthier than many other types of dairy as it has more nutrients, fewer calories and less saturated fat. However, all milk products contain lactose. According to a 2014 study in the British Medical Journal, too much lactose can be bad for your health. Longitudinal studies like these have shown that drinking large amounts of milk each day (three or more glasses) may even increase the risk of mortality.

Lactose creates byproducts in your body during the digestion process that have been linked to aging, heart disease and cancers, such as prostate cancer. However, drinking milk in moderation (one or two glasses each day) doesn't seem to have the same negative effects on health. Consumption of fermented milk products or lower-lactose products (like goat's milk or plant-based milks) can also be healthier alternatives.

Milk in Your Diet

According to the Dietary Guidelines for Americans, 3 cups of dairy each day is a healthy amount for most Americans to consume. Each cup of milk is the equivalent of 8 fluid ounces, or 245 grams. Based on these guidelines, this would mean you could consume 24 ounces (or 735 grams) of milk but no other dairy products.

The nutrient content of milk varies substantially based on the type of milk you're drinking. If you were drinking full-fat milk, 3 cups would contain:

447 calories (149 per cup)
36 percent of the daily value (DV) for fat, or 23.7 grams (7.9 grams per cup)
45 percent of the DV for protein, or 23.1 grams (7.7 grams per cup)
12 percent of the DV for carbohydrates, or 35.1 grams (11.7 grams per cup)

In contrast, skim and low-fat milks are good sources of protein, but have much lower fat content. Three cups of 1 percent fat milk have:

306 calories (102 per cup)
12 percent of the DV for fat, or 7.2 grams (2.4 grams per cup)
48 percent of the DV for protein, or 24.6 grams (8.2 grams per cup)
12 percent of the DV for carbohydrates, or 36.6 grams (12.2 grams per cup)

Three cups of skim milk have:

248 calories (83 per cup)
1 percent of the DV for fat, or 0.6 gram (0.2 gram per cup)
53 percent of the DV for protein, or 24.9 grams (8.3 grams per cup)
12 percent of the DV for carbohydrates, or 36.6 grams (12.2 grams per cup)

Nutritional Benefits of Drinking Milk

Milk is considered to be very rich in nutrients. Regardless of whether it's low fat or full fat, milk usually contains vitamins, such as vitamin A, B-complex vitamins and D, and minerals, like calcium, magnesium, phosphorus, potassium, selenium and zinc. Milk is also rich in lactose, although it may be present in varying amounts based on the source of your milk.

Three cups of milk would easily allow you to obtain the DV for nutrients like vitamins B2 and B12 and most of the DV for such nutrients as calcium, phosphorus and vitamin B5.

Gallon of Milk a Day

There are 16 cups or 4 quarts in a gallon (3.79 liters) of milk. If you were to consume a gallon of milk each day, you'd be consuming around five and half times the recommended amount.

A gallon of full-fat milk contains:

2,384 calories
126.4 grams of fat, where 73.6 grams come from saturated fat
123.2 grams of protein
187.2 grams of carbohydrates

A gallon of 1 percent fat milk contains:

1,632 calories
38.4 grams of fat, where 24 grams come from saturated fat
131.2 grams of protein
195.2 grams of carbohydrates

A gallon of skim milk contains:

1,328 calories
3.2 grams of fat, 1.6 grams from saturated fat
132.8 grams of protein
195.2 grams of carbohydrates

Milk and Recommended Macronutrients

Based on a standard 2,000-calorie-a-day diet, the Food and Drug Administration recommends that people consume 300 grams of carbohydrates, 50 grams of protein and 65 grams of fat. No more than 20 grams of fat should come from saturated fat.

Because there are 2,384 calories in a gallon of full-fat milk, drinking this amount in a day would be inappropriate if you were trying to follow a healthy diet. However, even if you were consuming a higher-calorie diet, a gallon of full-fat milk would be unsuitable for good health as it has too much saturated fat.

One percent milk also contains too much saturated fat. According to the American Heart Association, excessive saturated fat can increase your risk of conditions like heart disease and stroke. Given that it has the least calories and is low in both fat and saturated fat, the only milk that you could consume at the rate of a gallon a day is skim milk.

Large Amounts of Skim Milk

One gallon of skim milk might be the best type of cow's milk you could drink, but it still wouldn't be a healthy choice and contains lactose, like other milk products.

If you were to consume a gallon of skim milk, you'd be taking in excessive amounts of certain nutrients, particularly B-complex vitamins, calcium and phosphorus. A gallon of skim milk each day would also mean that you'd be consuming almost three times more protein than you need on a daily basis.

While consuming three times as much protein could be unhealthy, you can eat roughly this amount of protein each day to lose weight or build muscle if you're following a high-protein, low-fat diet. However, such diets typically direct you to consume fewer carbohydrates (around 170 grams per day). This means that consuming a gallon of skim milk a day wouldn't even be suitable for this type of diet.